The present invention relates to a filter cartridge for removing suspended foreign matter from circulating lubricant, and more particularly, to that type of cartridge composed of a stack of filter discs with intercalated spacer discs forming a hollow cylindrical package through which the lubricant to be clarified is caused to flow in a radial or contra-radial direction, as described in U.S. Pat. No. 2,687,805 issued to E. H. Proulx on Aug. 31, 1954 and assigned to the assignee of the present invention.
The present invention is an improvement relating to the structures disclosed in U.S. Pat. No. 3,360,133 issued Dec. 26, 1967 to E. H. Proulx and in U.S. Pat. No. 3,425,563 issued Feb. 4, 1969 to H. Wilansky, both of which are assigned to the assignee of this application.
As pointed out in the above-identified Wilansky patent, the lubricant to be clarified may be contaminated with water. Such contamination may be the result of condensation of water vapor during periods of shut down or by leakage from the cooling system of an internal combustion engine or turbine due to a faulty gasket or the like.
The spacer discs usually comprise a mixture of cotton fibre and cellulose fibre which is coagulated from an aqueous vehicle. These fibres are of a hygroscopic nature, tending to absorb and retain any water entrained in the contaminated liquid. The water so absorbed swells and softens the spacer discs, causing their edge portions to expand into and clog the inlet ports in the filter discs. The consequent resistance to flow of lubricant into the cartridge causes the external pressure to build up and augment the intrusion of the softened portions of the spacer discs into the inlet ports of the filter discs until warping or wrinkling of the discs takes place, thereby opening radial passages between the discs and suddenly permitting substantially free flow of the lubricant, still loaded with accumulated sludge and grit. Such violent breakdown of the filter may occur at pressure drops as low as 40 p.s.i. differential. This occurrence can quickly have a disastrous effect on the bearing surfaces of the unit being lubricated.
In accordance with the teachings of the aforementioned Wilansky patent, wire staples inserted circumferentially in the separator discs in position to register with the inlet ports of he filter discs restrain the swelling and intrusion of the material of the separator discs at these critical areas. The aforementioned Proulx U.S. Pat. No. 3,360,133 teaches the use of wire stitch reinforcements of the filter discs bridging the outlet ports of the spacer discs to prevent channeling, a condition whereby pressure due to the buildup of solid particles in the intake cells causes portions of the filter discs to be forced into the outlet passages, thereby permitting unfiltered oil to pass directly through the cartridge.
The combined features of the above-described Proulx and Wilansky patents have resulted in filter cartridges in which the disruptive type of failure due to water-contaminated oil has been effectively prevented even when the pressure drop has been permitted to increase to as much as 100 p.s.i. differential. Although the performance of this type of filter cartridge has been exceptional under such adverse conditions as continued use after recommended maximum pressure has been reached and filtration of water-contaminated oil, it would be desirable to simplify the construction of the discs employed in such cartridges, thereby reducing the manufacturing cost and time.